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REQUEST FOR COUNCII, ACTION Department Approval: DATE: 05/ 1 1 /Ol ITEM NO. : � _ 1 Agenda Section: Reports Item Description: Receive Drainage Study for Har- Mar Mall, CFL Building and Zimmerman Lake Area and Order Preparation of a Feasibility Report. Background: On May 7, 2001 the Council approved a Mn/DOT 7oint Powers Agreement for the preparation of a Drainage study of the Zimmerman Lake Area. H. R. Green, one of the City's Engineering Consultants, has completed this analysis of the Har- Mar Ma11; NTinnesota Department of Children, Families, and Learning (CFL) Building; and Zimmerman Lake Area. In order to better define this project we recommend that a feasibility report be prepared. The attached drainage study looked at the e�sting subwatershed for Zimmerman Lake and how it relates to the flooding in the neighborhoods east of Har- Mar Ma11 as well as the flooding of the ditch south of Hwy 36. The report identified that flooding in the Zimmerman Lake subwatershed could be resolved by increasing the culvert capacity under Hwy 36. We ha�e looked at this flooding as a subwatershed problem. The reasons for the flooding cannot be attributed to any one single cause. Mn/DOT installed the pipe under Hwy 36 in the late 1950's. The runoff that is ponding in the ditch is from 493 acres of land made up of residential, commercial and highway uses. There is no public drainage easement on the CFL building parcel to a11ow for the impoundment of water on their properiy. When the addition was constructed in 1978, there were no provisions made for the ditch runoff. There has been some development and redevelopment in the subwatershed over the last 50 years that could contribute to the overall quantity of water being conveyed to Zimmerman Lake. We ha�e met with CFL/Wellington Management, Mn/DOT, and the City of Falcon Heights to discuss the report and the possible solutions. We have also consulted Rice Creek Watershed District in a regulatory capacity. We are setting up a meeting with the University of NTinnesota to discuss the improvement. The alternative favored by the group is Option 3, detailed on page 8 of the report. This option would lower the flooding in the south ditch below the lowest floor elevation of the CFL building as well as eliminate the flooding of Eldridge Avenue east of Har- Mar Ma11. There would be a negligible increase to the elevation of Zimmerman Lake and other downstream